Closure plate for cargo tanker



y 18, 1965 w. H. GRAVERT 3,184,099

CLOSURE PLATE FOR CARGO TANKER Filed June 17, 1963 2 Sheets-Sheet 1 I5 w I00 William H. Graven- ATTORNEY y 1965 w. H. GRAVERT 3,184,099

CLOSURE PLATE FOR CARGO TANKER Filed June 17, 1963 2 Sheets-Sheet 2 l 13 INVENTOR 1 A William H. Graven ATTORNEY United States Patent 3,184,099 CLOSURE PLATE FOR CARGO TANKER William H. Gravert, Port Washington, N. assignor to Marine Moisture Control Company, Inc., Inwood, Long Island, New York, a corporation of New York Filed June 17, 1963, Ser. No. 288,862 4 Claims. (Cl. 2261-65) This invention relates to a closure plate of the type commonly known as a Butterworth cover for covering an aperture in the steel deck of a cargo tanker such as an oil tanker.

Ships for transporting oil or other fluid cargo are commonly provided with a number of large tanks below deck (typically 30 x 30 feet, and 60 feet deep), the deck of the vessel constituting the top cover of each individual tank. In the center of each tank cover section, a large covered aperture is provided for main access to the tank, which is sufiiciently large to accommodate a person desiring access to the interior of the tank for repairs, maintenance, etc. In addition to this, several smaller apertures, typically about a foot in diameter, are provided in the deck surrounding the cargo trunk through which buckets and tools may be lowered when necessary, and which are also used for venting potentially explosive gases from the interior prior to cleaning, by displacing such gases with inert carbon dioxide from the smoke stack. The deck covers closing the smaller apertures are commonly known as Butterworth covers, and have heretofore consisted generally of a gasketed metal cover plate fastened to the deck by approximately a dozen bolts protruding from the deck, which pass through holes near the edge of the plate, whereby the plate may be screwed firmly to the deck by means of the corresponding number of nuts. Mounting and removing these cover plates is therefore a tedious and slow job. Furthermore, the threaded bolts protruding from the deck eventually become rusted due to the action of salt water on them, and must be replaced, which is another tedious welding job, and can only be done when the tank is gas free; it takes a day to gas free a tank.

It is a primary object of the present invention to provide an improved cover plate for the above purpose which can be readily and safely fastened in place by a simple turn of a few latch members equi-distantly spaced around the circumference of the plate.

It is a further object of the invention to eliminate the need for bolts or any other members fixed to the deck, and to provide a self-contained cover plate which itself contains all of the fastening elements required to secure in place. Thus, any of the latching element should become damaged or deteriorated, it can be replaced by another cover plate without the necessity of performing any operation on the ships deck.

Another object is to provide a latching plate having latch-operated means on the top side of the plate which extends through the plate in sealed relationship so that there is no possibility of inflammable liquid or explosive fumes escaping from the tank.

A further object is to provide a cover plate of the type described, with latching means capable of being adjusted to accommodate various deck thicknesses over a wide range.

In accordance with the invention, a gasketed cover plate is provided with cam latching means essentially similar to those described in US. patent to Gravert, No. 2,996,318 for Cam Operated Quick Acting Pipe Coupler. This particular type of cam latch has the advantage for the present purpose of providing a camlatch bearing surface which is in contact with the element which it engages over a large area, and not merely at a single point as in conventional cams. Adjustable spacer means Eddkfi Patented May 18, 1965 ice are provided on the cam shaft, which by a simple transposition can be put on either side of the cam so as to adjust it for engaging decks of various thickness over a much wider range than the slope of the cam itself permits. The cam shaft is also provided with special sealing means to ensure no leakage of fluid or gas through the cam mechanism itself. The cam shaft is also provided with indicating means for indicating the open or closed position of the latch, since this cannot be seen from the exterior.

The specific nature of the invention, as well as other objects and advantages thereof, will clearly appear from a description of a prefer-red embodiment as shown in the accompanying drawing, in which:

FIG. 1 is a top plan view of a cover according to the invention installed on a deck;

FIG. 2 is a sectional view taken on line 2-2 of FIG. 1;

FIG. 3 is a detail view of a cam latch and portion of the associated cover, taken in the direction of the arrow A in FIG. 2; and

FIG. 4 is a detailed view of a cam latch showing the manner in which it is adjusted to accommodate a greater plate thickness.

Referring to FIG. 1, the deck 2 of the vessel serves also as the top side of the storage tank, and is provided with a number of apertures which are to be covered with the cover plates of the invention, only one such aperture 3 being shown. Cover plate 4 overlies and seals aperture -3, and is provided with a suitable number, for cx ample three, equi-spaced camlatches ro-tatably controlled by the rotary position of protruding control element 6, of which there is one for each cam latch. These control elements are preferably provided with pointer means 7 which cooperate with suitable indicia on the cover to show whether the cam latch is in the open or closed position.

As best shown in FIG. 2, the under side of the cover plate 4 is provided with a suitable groove 10 near its rim for retaining a large O-ring 10a which serves as a gasket providing a tight seal between the cover and deck when the cover is clamped into place.

Control element 6 is provided with an aperture 8 through which a metal bar or pin can be inserted to provide sufficient force for tightening the cam latch when necessary. The control element is fixed to a shaft 9 rotatable in a suitable circular aperture drilled through the cover 4. O-rings 15 are seated in suitable gnooves in the shaft in order to effect a tight seal between the shaft and the cover plate 4 to prevent any possibility of leakage from the interior of the tank between the shaft 9 and its associated aperture. Addition-ally or alternatively, gasket 5 may be placed under shoulder 5a, where it will be compressed by the clamping section of the cam lock to provide a very tight seal. Shaft 9 has an extension 12, preferably somewhat reduced in diameter, to which is fixed cam latch 13, as by set screw 14 cooperating with axial groove 16 in extension 12, or by using a square shaft and square holes. Two washers or circular shims 17 and 18 are also held on extension 12, the entire assembly above described being held together in any suitable manner, as by nut 19 screwed onto thread 21 at the end of the shaft extension, and preferably firmly held against rotation as by cotter pin 22.

The washers 17 and 18 may be of equal thickness, but are preferably of different thicknesses to provide for a greater width of adjustment. If the deckplate 2 is of greater relative thickness than shown in FIG. 2, shim 17 may be moved from the position shown in FIG. 2 to that shown in FIG. 4, in order to increase the effective clamping space of the cam; If still greater thickness is desired, the thicker washer 18 may be used instead, or for maximum thickness, both washers together may be moved between the cam and the cover plate. The washer shims thus provide for a greater range in deck thicknesses than can be .efiiciently taken care of by the cam slope itself. In ship practice, the deck plates may run between inch and 1% inches in thickness, which can readily be taken care of by two washer shims as shown. FIG. 4 shows the cam in the locked position, which the indicator point 7 on the control element shows by pointing in a generally outward position. If the control element is rotated 180 from the position shown in FIG. 4, it will be apparent that side 13a of the cam will be opposite the edge of the deck, providing ample clearance for removing the cover from the deck aperture. 7

When the cam lock is viewed at 90 from the position shown in FIG. 4, it will appear as shown in FIG. 3 to be somewhat tilted with respect to the cover 4. This is done for essentially the same reason as explained in US. Patent No. 2,996,316 of Gravert, in order'to secure a large bearing surface between the cam and the underside .of'the deck plate 2. 'This is'accomplished by making the. axial tilt of shaft 9 with respect to the cover deck to have the same angle as the ramp slope of the cam, so that the upper surface of the cam at the point of engagement with the deck is substantially parallel tothe lower surface of the deckplate. In this manner, a maximum bearing surface is obtained, which is of value since it permits the use of only three cam locks to secure adequate sealing force which previously required a dozen or so separate nuts and bolts.

It will be apparent that the embodiments shown are only examplary and that various modifications can be made in construction and arrangementwi-thin the scope of my invention as defined in the appended claims.

I claim:

1. For use with a smooth, unobstructed portion of a ships deck of thick steel plate having an orifice, an orifice cover comprising a removable metal cover plate; a continuous gasket firmly held on the underside of said cover plate for sealing said plate again-st said Wall; and

. cam pressure clamping means for securely seal-ingsa-id for rotating said. shaft, cam means rotatable with said shaft for clampingly engaging said deck between the under sideof said cover plate near the rim thereof and the cam face of said carn means, as said shaft is rotated; sealing means between said rotary means and said cover plate for preventing the passage of fluid or gas, said sealing means comprising at least one O-ring in an annular groove in said shaft andengaging the :wall of said aperture.

2. A closure for an orifice in a thick metal wall comprising a removable metal cover plate; a continuous gasket on the underside of said cover plate for sealing said plate against said wall; and cam pressure clamping means for securely fastening said cover plate in place under sufiicient pressure to efiectively compress said gasket between the cover plate and the wall, said clamping means comprising 7 rot-arymeans including a rotatable shaft passing through a circular aperture in said cover plate nearthe rim thereof, a rotation control element fixed to said shaft on the outer side of said cover plate for rotating said shaft, cam means rotatable with said s'haft for clampingrly engaging said metal wall between the underside of said cover plate near the rim thereof and the cam face of said cam means, as said shaft is rotated, said shaft extending through and beyond said cam means, said cam means being axially slida'ble with respect to said shaft but angularly fixed to the shaft for rotation therewith, retaining means at the end of said shaft for retaining said cam means thereon, and shim washer means loosely mounted on said shaft between said retaining means and said ca-m means, said shim lw-asher'rneans being removable on said shaft to the opposite side of said cam means to enlarge the eifective gap of said cam means for engaging a plate of greater thickness than allowed by the initial gap of said cam means.

3. The invention according to claim 2, said control element having a'horizontal aperture therethrough for reception of a force-applying lever.

4. The invention according to claim 2, said shim washer means comprising two shim washers of different thickness.

7 References Cited by the Examiner UNITED STATES PATENTS THERON E. CONDON, Primary Examiner EARLE J. DRUMMOND, Examiner. 

1. FOR USE WITH A SMOOTH, UNOBSTRUCTED PORTION OF A SHIP''S DECK OF THICK STEEL PLATE HAVING AN ORIFICE, AN ORIFICE COVER COMPRISING A REMOVABLE METAL COVER PLATE; A CONTINUOUS GASKET FIRMLY HELD ON THE UNDERSIDE OF SAID COVER PLATE FOR SEALING SAID PLATE AGAINST SAID WALL; AND CAM PRESSURE CLAMPING MEANS FOR SECURELY SEALING SAID COVER PLATE IN PLACE AGAINST THE SMOOTH TOP SIDE OF THE DECK UNDER SUFFICIENT PRESSURE TO EFFECTUALLY COMPRESS SAID GASKET BETWEEN THE COVER PLATE AND THE DECK, SAID CLAMPING MEANS COMPRISING ROTARY MEANS INCLUDING A ROTATABLE SHAFT PASSING THROUGH A CIRCULAR APERTURE IN SAID COVER PLATE NEAR THE RIM THEREOF, A ROTATION CONTROL ELEMENT FIXED TO SAID SHAFT TO THE OUTER SIDE OF SAID COVER PLATE FOR ROTATING SAID SHAFT, CAM MEANS ROTATABLE WITH SAID SHAFT FOR CLAMPINGLY ENGAGING SAID DECK BETWEEN THE UNDER SIDE OF SAID COVER PLATE NEAR THE RIM THEREOF AND THE CAM FACE OF SAID CAM MEANS, AS SAID SHAFT IS ROTATED; SEALING MEANS BETWEEN SAID ROTARY MEANS AND SAID COVER PLATE FOR PREVENTING THE PASSAGE OF FLUID OR GAS, SAID SEALING MEANS COMPRISING AT LEAST ONE O-RING IN AN ANNULAR GROOVE IN SAID SHAFT AND ENGAGING THE WALL OF SAID APERTURE. 